Packings are used to prevent or minimize the leakage of fluids through the mechanical clearances usually present in fluidic equipment. Such clearances may exist in either the static or dynamic state. Generally, gaskets are installed in static clearances normally existing between parallel flanges or concentric cylinders; whereas for moving surfaces, dynamic packings are employed to fill mechanical clearances.
In functioning, to retain fluid under pressure, dynamic packings carry the hydraulic load. When no pressure exists, as in many oil-seal applications, the packing is mechanically loaded as by a spring or by its own resiliency. Dynamic packings therefore operate as bearings, thus indicating the need for lubrication to serve as both a separating film and a coolant. While the presence of such a film is vital for satisfactory service life, it also means that leakage will occur. Low-viscosity fluids and high pressures add to leakage problems, as both require thin films to minimize leakage. This causes higher friction and results in heat, which is the one most detrimental factor in packing life. Normally the fluid being sealed serves as the lubricant. Thus, where oils are involved, maximum efficiency is obtained. Next in order are clean water, solvents, and fluids, containing solids which progressively yield more unsatisfactory results unless supplemental lubrication is provided. While various types of dynamic packings exist, soft or jamb packings are best suited for rod or plunger service, since an adjustable gland is required. Many materials are employed, such as braided flax saturated with wax or viscous lubricants for water and aqueous solutions; braided asbestos similarly treated or often impregnated with polytretrafluoroethylene suspensoid for superior life under severe service conditions; laminated rubberized cotton fabric for hot water, low-pressure steam and ammonia; rolled rubberized asbestos fabric for steam; and rolled or twisted metal foil for high-temperature and high-pressure conditions. Packings containing woven or braided asbestos fibers are also made from wire-inserted yarns to gain additional strength.
Rotary shafts are generally packed with adjustable soft packings. The soft packings are of the same general type as those used for reciprocating service, with the asbestos braid lubricated with grease and graphite or with polytetrafluoroethylene suspensoid. The latter is the most popular for typical applications on centrifugal pumps and valve stems. For continuous rotary service, automatic packings are best restricted to low pressure because their tightness under high pressure tends to cause overheating. However, for intermittent servie, as on valve stems, they are excellent.
In hydrocarbon refineries, petrochemical plants, and in the exploration and production of oil and gas, there are valves, pumps, and other equipment which utilize soft packing as a sealing media. These soft packings, which are typically graphite or teflon impregnated cord, have a limited service life and must be replaced. Replacement of such packing requires that the equipment be taken off line. Further, removal of the packing is often a time consuming process, resulting in high maintenance costs, equipment downtime and lost profitability.
To address the problems associated with the replacement of packing material, several improvements in equipment design have been proposed, as evidenced by U.S. Pat. Nos. 4,135,541 and 2,809,059, which are hereby incorporated by reference. While such designs may be beneficial, much of the equipment still utilized today requires the conventional, time-consuming manual replacement of soft packing.
While gaining access to the soft packing consumes a large portion of the time associated with packing replacement, the removal of the packing from the packing box itself is highly time consuming. Generally, to remove the packing a tool which may either resemble an ice-pick or a cork screw is used. Such a tool is worked into the packing material and the packing picked out. As those skilled in the art recognize, this is a tedious exercise which is made all the more so by the fact that one cannot gain a firm hold of the packing material after inserting such a tool. Several attempts are often required since the packing material often slips off of the tool.
Therefore, what is needed is a packing removing tool of improved design which is capable of reducing the time required to remove soft packing from valves, pumps and other such equipment.